16. Johnson Robert, Life Without Parole, Our Other Death Penalty: Are Life-Sentenced Inmates a Danger to Others in Prison?, Oral Testimony. Annapolis, Maryland September 22, 2008. Źródło: http://www.goccp.maryland.gov/capital-punishment/documents/johnson-testimony.pdf.

47. Sattar Ghazala, Rates and causes of death among prisoners and offenders under community supervision, Home Office Research Study 231, 2001, s. 4. Źródło: http://library.npia.police.uk/docs/hors/hors231.pdf